1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) device, and particularly, to an LCD device capable of minimizing the number of optical sheets provided to enhance optical uniformity by implementing uniform brightness of light supplied to an LC panel, and capable of requiring no light shielding unit, the light shielding unit disposed on a region near an optical source so as to be printed on the optical sheet, or additionally provided for prevention of non-uniform brightness.
2. Background of the Invention
In general, a liquid crystal display (LCD) device is being widely used due to advantages such as a light weight, a thin thickness, and low power consumption. Accordingly, the LCD device is being widely used to display images on screens of a portable computer such as a notebook PC, an office automation equipment, an audio/video apparatus, etc.
The LCD device displays desired images on a screen by controlling optical transmittance according to image signals applied to a plurality of controlling switching devices arranged in a matrix format.
The LCD device comprises an LC panel and a driving portion. The LC panel includes an upper substrate, a color filter substrate facing a lower substrate, a thin film transistor (TFT) array substrate, and an LC layer sandwiched by the upper and lower substrates. The driving portion drives the LC panel by supplying scan signals and image information to the LC panel.
Since the LCD device does not spontaneously emit light, it is provided with a light source to supply light to the LC panel so as to implement an image. Accordingly, the LCD device is provided with a backlight assembly including a light source to supply light to the LC panel.
Hereinafter, the conventional LCD device will be explained in more detail with reference to the attached drawings.
As shown in FIG. 1, the conventional LCD device comprises an LC panel 1, a lamp 2 disposed at one side below the LC panel 1, for supplying light to the LC panel 1; a lamp housing 7 configured to encompass and protect the lamp 2, and having an opening; a light guide plate 3 disposed at one side of the lamp 2, for guiding light emitted from the lamp 2 to the LC panel 1; a plurality of optical sheets 5 disposed on the light guide plate 3, for converting light emitted from the light guide plate 3 and supplying it to the LC panel 1; a light shielding unit 13 disposed or printed on an uppermost optical sheet among the plurality of optical sheets; and a reflection sheet 6 disposed under the light guide plate 3, for reflecting light that has leaked to a lower side of the light guide plate 3 into the light guide plate 3.
In the conventional LCD device, light emitted from the lamp 2 is preferably made to be incident on an inner side of the light guide plate 3, and then to be totally-reflected a plurality of times. However, some of light is reflected to the lamp housing 7 or the reflection sheet 6 only one or two times, and then is emitted to outside of the light guide plate 3. The emitted light is observed as bright lines as shown in regions ‘A’ and ‘B’ of FIG. 2.
Furthermore, the conventional LCD device may be provided with light emitting diodes rather than the lamp, as an optical source. In this case, some of light emitted from the light emitting diodes is reflected one or two times, onto a printed circuit board or a reflection sheet on which the light emitting diodes are mounted. Then, the reflected light is emitted to outside of the light guide plate, which is observed as bright points as shown in a region of ‘C’ of FIG. 3.